FR2577719A1 - POLARIZATION DUPLEXER - Google Patents

Abstract

DEVICE ALLOWING TO EXTRACT OR EXCITE THE TWO ORTHOGONAL COMPONENTS OF THE FUNDAMENTAL MODE SPREADING IN A WAVE GUIDE WITHOUT AFFECTING THE OTHER FREQUENCY BANDS THAT MAY ALSO SPREAD THERE. IT INCLUDES A MAIN GUIDE 1, A TRANSITION 2 TO ANOTHER CONTIGUOUS GUIDE 3 OF LOWER DIMENSIONS BRINGING A SHORT-CIRCUIT PLAN 4, AND TWO ACCESS GUIDES 5, 6 ORTHOGONAL. THE COUPLINGS ARE MADE BY SINGLE RESONANT SLOTS 7, 8, AND A LOW PASS FILTER 9, 10 IN EACH ACCESS BRANCH SHORTS THESE SLOTS A SHORT CIRCUIT FOR FREQUENCIES OUTSIDE THOSE OF THE BASIC MODE OF THE MAIN GUIDE 1.

Description

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  The present invention relates to a device for

  to extract or excite the two orthogonal components of the basic mode of

  mental propagating in a waveguide without affecting other frequency bands that may also spread. As regards polarization duplexer, the orthomode duplexer is known which comprises a main guide, in the axis of which is placed a short circuit board, and another guide, said parallel access guide, orthogonal of the first and placed in a critical position with respect to this short circuit blade. This very classic device

  has the disadvantage of being limited to the use of a single frequency

  frequency or frequency band, since the other frequencies or

  frequency bands can not propagate beyond this device.

  In addition, a duplexing device is known as described

  in European Patent Application No. 98192, which includes a main guide

  cipal carrying both the frequency or frequency band to be multiplexed than other frequency bands, in particular a higher frequency band, and two access guides orthogonal to the main guide and orthogonal ones between them which are coupled to the main guide

  by slots filled with resonators.

  In this embodiment, the access guides are not coplanated.

  are associated with short-circuit devices placed in

  the main guide and which consist of quasi-optical filters

  c. The use of these quasi-optical filters in this kind of dis-

  positive has the disadvantage of requiring a study and a rather delicate focus. Moreover, this kind of filter is not a

  material that can be directly embedded on a satellite.

  Moreover, this type of device uses resonators, placed at the location of each of the coupling slots, which are also elements of delicate development and of an empirical character and which,

  because they are likely to break under the influence of vibra-

  tions are hardly conceivable for the production of

embedded on satellite.

  The present invention relates to a device as above

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  -2- defined that does not have the disadvantages of known devices juqu'alors. In particular, such a device is particularly well adapted to withstand the mechanical stresses required by a satellite boarding and it also allows, by cascading several devices of this type, to perform the excitation or

  the extraction of several frequencies or frequency bands.

  The invention thus relates to a device for extracting

  or to excite the two orthogonal components of the fundamental mode

  propagate in a waveguide at a given frequency or frequency band. Such a device is of the type comprising a main guide, corresponding to said fundamental mode, and two access guides orthogonal to the main guide and orthogonal to each other, said access guides being either coplanar or distant by a half-length of wave in the guide or a multiple of this half-wavelength, and is characterized in that each of the access guides is coupled to the main guide by a simple resonant slot containing no other element, in that each of said access guides comprises a filter for selecting said frequency or frequency band, said filter being constructed so as to reduce substantially to said resonant slot a short circuit for the external frequencies to

  said frequency or frequency band, and in that said main guide

  The invention comprises a short-circuit device located, relative to the access guides, on the side opposite to the radiating element, said short-circuit device being constituted by a transition, or the like, between the main guide and a control guide. smaller transverse dimensions

  located contiguously to said main guide.

  the invention will be better understood by means of the following description:

  an exemplary embodiment, with reference to the single figure

  annexed diagrammatically, and in a side view, a provision

  of excitation and extraction of the two orthogonal components of the

  fundamental mode propagating in a guide.

  In the figure, the reference 1 designates what we will agree

  call the main guide, which in this example is a circular guide

  which fundamental mode corresponds to the frequency of 19 Gigahertz, for example. The upstream portion of the guide 1, on the left in the figure, is connected in a manner not shown, but known per se, to a radiating element such as a horn equipping an antenna on board a telecommunications satellite. The downstream portion of the guide 1 is extended, via a conical transition 2, by another circular guide 3 whose fundamental mode corresponds to a frequency greater than that of the guide 1, for example 28 Gigahertz to fix ideas. In a manner known per se, the transition 2 is equivalent, for the fundamental mode of the guide 1, to a short circuit located in a fictitious short-circuit plane 4. Of course, the transition 2 could be steep instead of concrete, or could be replaced by an equivalent device creating a fictitious short-circuit plan, such as a device

with cavity (s).

  According to the invention, two access guides (5, 6) coplanar in the example in question, orthogonal to each other and orthogonal to the main guide 1, rectangular in this example, and operating at the same frequency as the main guide 1, are each coupled to said main guide 1 by respectively a resonant slot (respectively 7 and 8). As seen in the drawing, each guide (5 or 6) is connected to the associated resonant slot (7 or 8) via a filter (respectively 9 and 10). Each filter (9 or 10) is, in the example

  considered a low-pass filter which cuts all the higher frequencies

  than that corresponding to the fundamental mode of the guide 1, that is 10 Gigahêrtz. Moreover, this filter is conventionally sized so as to reduce substantially, on the associated coupling slot, 7 or 8, a short circuit for all the frequencies

  above the frequency considered, of 19 Gigahertz in our example

  ple. For example, we will use a corrugated filter, well used in

this technique. -

  The operation of the device which has just been described is as follows: From the receiving aerial arrive for example, firstly two orthogonal polarization waves at the frequency of 19 Gigahertz and, secondly, two waves of orthogonal polarizations at the frequency of 28 Gigahertz. The waves at the lower frequency, that is to say 19 GHz, propagate in the circular guide 1 according to

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  its fundamental mode and according to two orthogonal polarizations. For example

  the first polarization is located in the plane of the figure and the

  second polarization is perpendicular to this plane.

  At the moment these orthogonal waves with a frequency of 19 Gigahertz arrive

  wind at the two coupling slots 7 and 8, a first part thereof is derived, by the coupling slots 7 and 8, towards the

  filters 9 and 10 respectively, and thus the access guides 5 and 6 respectively.

  tively. In the example considered, the polarization wave located in the plane of the figure is partially directed towards the guide 6 through

  the resonant slot 8 sized to resonate at the frequency considered

  Derived from 19 Gigahertz. Similarly, the polarization wave orthogonal to the plane of the figure is partially directed, in the same way, towards the

guide 5.

  The part of the two 19 Gigahertz waves which is not directed towards the guides 5 and 6 continues to propagate in the guide 1, then in the first part of the transition 2, in which it is reflected at the location of the short circuit plane 4, to return to the coupling slots 7 and 8 which then direct them to the guides 5 and 6, as explained above. The part of the wave, moreover negligible in practice, which is not directed at this moment towards the guides 5

  and 6, is then reflected to the radiating element.

  Of course, the distance between the short circuit plane 4 and the radiating slots 7 and 8 is adjusted conventionally so that a maximum of reflected waves is absorbed by the access guides 5

and 6.

  The two orthogonal waves whose frequency (28 Gigahertz) is greater than the frequency of the fundamental mode of the guide 1 propagate in this guide 1 without being derived by the couplers 6 and 7, which are, moreover, vis-à-vis of this frequency, like short circuits, then in transition 2, to continue their route

  in Guide 3 to a possible second separation device similar to

  to the one just described.

  It will be noted with interest that the higher frequency waves (28 Gigahertz in the example under consideration) propagate in the guide 1 without being substantially affected by the presence of the slots 7 and 8,

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  which, because they form a short-circuit for these frequencies,

  have virtually no existence from the electrical point of view.

  In the example considered, the two access guides 5 and 6 are coplanar. It is obvious that the device would work the same if one of the access guides, 5 or 6, was located, upstream of the other, at a distance of the latter equal to one or more times the

  half-wavelength corresponding to the fundamental mode of the guide 1.

  The device that has just been described is capable of a number of interesting applications. For example, it is possible to couple the inputs 11 and 12 of the access guides 5 and 6, that is to say the inputs located opposite the coupling slots 7 and 8, to the two outputs of a 3dB hybrid coupler. This allows, in the case where one receives in the main guide 1 a circularly polarized wave, to obtain at the opposite input of said coupler the corresponding linear polarization, and vice versa in the case of transmission. A polarizer has thus been constituted without intervening on the main guide 1. This same device, envisaged only on reception, also makes it possible to obtain a constant reception level regardless of the direction of reception.

linear polarization received.

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Claims (2)

  1 / Device for extracting or exciting the two orthogonal components of the fundamental mode that can propagate in a waveguide at a given frequency or frequency band, of the type comprising a main guide (1) corresponding to said fundamental mode, and two access guides (5, 6) orthogonal to the main guide and orthogonal to each other, said access guides being either coplanar or half a wavelength apart in the guide or a multiple of this half wavelength, characterized in that each of the access guides (5, 6) is coupled to the main guide (1) by a simple resonant slot (7, 8) having no other element, in that each of said access guides (5, 6) comprises a filter (9, 10) for selecting said frequency or frequency band, said filter being   constructed so as to reduce substantially to said resonant slot   a short circuit for frequencies outside that frequency   quence or frequency band, and in that said main guide (1) comprises a short-circuit device located, relative to the access guides, the side opposite to the radiating element, said short-circuit device being constituted by a transition (2), or the like, between   the main guide (1) and a smaller cross-sectional guide   sales (3) located contiguously to said main guide.   2 / Apparatus according to claim 1, characterized in that it comprises   furthermore, a hybrid coupler having each of its outputs coupled   the outputs (11, 12) of said access guides (5, 6).